This is tough, both C and D look good. But, I think C is wrong because it seems that the modifier "Although widely distributed" is actually modifying "lesser cornstalk borer control" as opposed of just modifying "lesser cornstalk borer".
1000SC is a banned source because it illegally uses copyrighted problems without permission. (And, even if it didn't, we'd ban it anyway - a lot of the problems in the set are fine, but there are a number of bad ones that can actually mess up your study if you use them!)